Evolutionary ecology of pipefish brooding structures:embryo survival and growth do not improve with a pouch

For animals that reproduce in water, many adaptations in life-history traits such as egg size, parental care, and behaviors that relate to embryo oxygenation are still poorly understood. In pipefishes, seahorses and seadragons, males care for the embryos either in some sort of brood pouch, or attached ventrally to the skin on their belly or tail. Typically, egg size is larger in the brood pouch group and it has been suggested that oxygen supplied via the pouch buffers the developing embryos against hypoxia and as such is an adaptation that has facilitated the evolution of larger eggs. Here, using four pipefish species, we tested whether the presence or absence of brood pouch relates to how male behavior, embryo size, and survival are affected by hypoxia, with normoxia as control. Two of our studied species Entelurus aequoreus and Nerophis ophidion (both having small eggs) have simple ventral attachment of eggs onto the male trunk, and the other two, Syngnathus typhle (large eggs) and S. rostellatus (small eggs), have fully enclosed brood pouches on the tail. Under hypoxia, all species showed lower embryo survival, while species with brood pouches suffered greater embryo mortality compared to pouchless species, irrespective of oxygen treatment. Behaviorally, species without pouches spent more time closer to the surface, possibly to improve oxygenation. Overall, we found no significant benefits of brood pouches in terms of embryo survival and size under hypoxia. Instead, our results suggest negative effects of large egg size, despite the protection of brood pouches

Sperm displacement behavior of the cuttlefish Sepia esculenta (Cephalopoda: Sepiidae)

Sperm displacement behavior of cuttlefish (Sepia esculenta) was observed in a tank. Before ejaculation, male cuttlefish used their arms III to scrape out sperm masses attached to the buccal membranes of females. The removed sperm mass debris was directly visible and countable. Active sperm were present within the removed sperm debris, implying that the aim of this behavior is to remove competing male sperm. However, many sperm masses remained on the female buccal membrane even after the removal behavior, showing that sperm removal in S. esculenta is incomplete. The duration of sperm removal (an indicator of male investment in that process) was unaffected by the body sizes of mated pair, the duration of spermatangia placement at the current mating (for the hypothesis that the sperm removal serves to creat attachment space of spermatophores), or the estimated amount of sperm masses deposited from previous matings. Moreover, male S. esculenta performed sperm removal regardless of whether the last male to mate with the partner was himself, suggesting males remove not only the sperm of rivals but also their own. Although the number of removed sperm masses increased with the time spent on removal of sperm, male cuttlefish may shorten the duration of sperm removal to avoid the risk of mating interruption. We conclude that this time restriction would likely influence the degree of partial sperm removal in S. esculenta. A digital video image relating to the article is available at http://www.momo-p.com/showdetail-e.php?movieid=momo040729se01a

Sperm removal by dusky frillgoby

Analysis code; Paternity data; Concentration data; Compensation data; Faning duration data; Occurrence of fanning dat

Early filial cannibalism revisited from an endocrinological perspective

Offspring desertion by parents generally occurs at an early stage of parental care, which is considered to minimize the time and energy costs of parental care prior to desertion and ensure an opportunity and time for future reproduction. In addition to these conventional reasons, we investigated the effects of endocrinological constraint on early total filial cannibalism in fish in which care-giving males eat all eggs and restart reproduction when tending a small number of eggs. The occurrence of total filial cannibalism in male Rhabdoblennius nitidus, a paternal brooding blennid fish with androgen-dependent brood cycling, was strongly associated with decreased plasma 11-ketotestosterone levels, suggesting that males in which it was difficult to exhibit courtship behavior began to cannibalize eggs. Moreover, the additional mating probability at the beginning of parental care may delay the timing of total filial cannibalism; at the same time, the costs of parental care may shift the timing earlier than expected based on androgen decline. These results suggest the potential importance of considering endocrinological constraints with respect to the adaptivity of behavioral traits.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Sperm removal by dusky frillgoby

Raw data of paternity analysis; Raw data of compensatory behaviour analysi

Timing of sneaking behavior in the dusky frillgoby Bathygobius fuscus sneaker males

Sneaking is a parasitic reproductive behavioral tactic for stealing fertilization opportunities from other males that monopolize females; therefore, sneaker males always face sperm competition. The timing of sneaking is an important trait that contributes to their fertilization success. In the dusky frillgoby Bathygobius fuscus, an intertidal gobiid fish, spawning between a nest-holding male and a paired female continues over several hours. We investigated the behavior of sneaker males of this species in the wild by examining the number of sneaker males around the nest, aggressive interactions between sneaker males, sneaking attempts, and sneak intrusions as indices of their sneaking motivation. Pair spawning lasted for 23.7–192.8 min, during which a maximum of 0–23 sneaker males were observed around the nests. All indices of sneaking motivation, except the number of sneak intrusions, significantly decreased with time elapsed since the pair spawning began. This suggests that sneaking motivation was high at the early stage of pair spawning. Early sneaking may contribute to high fertilization success of sneaker males, likely owing to the long-surviving effect of their long-lived spermTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Filial cannibalism by male fish as an infanticide to restart courtship by self-regulating androgen levels

Raw data of egg-manipulation experiments; Raw data of the relationship between male body condition and types of filial cannibalis